Autoclave



Oct. 24, 1950 E. R. scHlPANsKl I 2,525,974

AuTocLAvE Filed sept. 11, 194e 2 sheets-sheet 2 a M15 I 5MP. 5:7' 4 TIM/2 5:7'

Patented Oct. 24, 1950 r UNITED STATES PATENT oFFlcE AUTOCLAYE Emil R. Schipanski, Gardena, Calif. Application September 11, 1946, SerialNo. 696,290

2o claims. (C1. ,2r-9s) 1 My invention relates generally to equipment for sterilizing surgical gowns, dressings, instruments, and the like, and more particularly to autoclaves wherein"su`ch'steiliaation is accomplished by the use :of`steanfinnderv pressure.A

Autocl'aves ior'the .aboiiepnrpose have usually been constructed principally' :from heavy metal castings with 'the steamfliyiies'as'sociated therewith mounted on'the, "tsdlof fthe device. Such construction'is costly requires considerable hand work on eachhin ividual piece of apparatus. l'urther'more; the useoff/ heavy castingsmakes diicult the use of adequate insulation and the Y devices so constructed are' ineiiicient for this reason and for the further reason 'that largefmasses of metal must .be heated addition `to the material being sterilized.' Furthermore, when uninsulated steam lines .arer'iin on ,the outside of the apparatua' and hence' subjected to room temperature, .there is ia marked .tendency Afor steam `to condenser Vwithin the passages so exposed, which condensation leads tomidiiiiculties in operation arisingfromcorrosion, .hydraulic ram effects, and injury to .pressure voperated valves andgauges.`

Another deficiency `often :encountered in previous apparatuslof thehclass described arises from the fact that the Vgenerally acceptedconstruction provides separate controls for controlling the heat applied to J`the steamboiler anddischarging steam from the Asterilizatirm chamber.

With a view'to overcoming the foregoing deiiciencies it is a majorobject of .my'inventionto provide autoclave construction .which makes possible the use of sheet metal parts and eicient insulation.

It is another `obj ect of my invention to provide passages for live steam which are integral wii the structure and avoid the harmful effects of condensation previously described.

Still another object of my invention is to .provide .multiple steam passages thereby reducing the possibility of plugged steam lines and the consequent danger to operating personnel.

A further object of myinvention is to provide a sterilization chamber which conforms to the general shape of laboratory packs 4of surgical dressings and the like, hencemaking economical use of the volume available.

Still another object of my invention is to provide a liner for the sterilization chamber of an autoclave which is readily removable forrepair or replacement.

An additional object of my invention is to provide for coordination of the boiler heat and steam discharge controls whereby to materially reduce the possibility of injury to operating personnel and damage to the equipment occasioned by boiling away the contents of the boiler.

' The foregoing and other objects and advantages of my invention willlbecomer'apparent from a. consideration of the following detailed description taken 1n connection with the attacheddrawings in which: t Y

Fig. l is a perspective view of an autoclave embodying my invention; v `4 F1g. 2 1s an' elevational section taken on the line 2 2 in Fig. l;

Fig is an elevational section taken on the line 3 3 in Fig'. 2;`V t Y 1.

Fig. 4 is a partial perspective view showing the system of discharge lines Y 1 t my invention, the chamber having a. generally` square transverse cross-section and being formed with a removable liner I9, access being provided thereto through a square door l l, The door Il is provided with a pressure proof gasket I8 Vand is secured against `pressure in the sterilization chamber l@ by means of a screw I3 having a hand wheel i144 keyed thereto. The pressure screw I3 is threadedly engaged with a nut ,I5 which, in turn, is held in the center of a transverse strong back l2. As can be seen in Fig. l the right end of the strong back I 2 is hingedly supported by gudgeons 'H at its right end, and is secured by a latch 12 at its left end. As indicated in Fig. 6 the latch '52 is mechanically linked to a line switch Se so that lunlatching the door 'I l `auto'- inaticallybreaksthe power circuit. The door vIl is supported by a centrally mounted foot l1 secured thereto and rotatably mounted .tothe forward end ofthe pressure screw I3.` An anti-friction bearing l5 is provided at the forward end of the pressure screw i3, and transmits the thrust of the screw to the foot l] and hence to the center of the door H. When the latch 1.2 is disengaged from the strong back l2, .thelatter may be swung back, carrying' the door Il therewith, andl giving access to. the chamber l0. "i

. An outer covering for the apparatus is provided in thel form of a tubular 'housing 11 closed attthe rearward end by a back' cover plate 1.3 and by Aa front cover plate 76 at the forward end. As can be seen in Fig. 5, the front cover'is brazed toa hollow door frame l5 and thus hermetically seals a passage formed .in 'the interior thereof. The

. back cover platel is secured in placeby means of screws 'i4 which are threaded' into'suitable holes formed in the ends of'tiebolts 36. "The bottom of the outer housing vTl is reinforced by a plate 84 suitably secured'thereto and is'further providedY with four supporting feet '83.v

ampleved in .the appa- Steam to effect sterilization of material loaded into the chamber l0, is produced in a boiler 23, a sump 24 of which depends from the rear bottom surface of the device, as best seen in Fig. 2. The steam pressure chamber includes the sump 24 and the generally tubular chamber surrounding the sterilization chamber I and is enclosed by a pressure wall 25. The bottom of the sump 24 is provided with a suitable drain plug 85 by which the boiler may be drained when necessary. The pressure wall 25 is secured at its forward end by brazing or other suitable means, to the hollow frame which surrounds the square opening in' the front cover plate 16 adjacent the door Il. A removable head 35 forms a closure for the rear of the pressure wall and is secured thereto by the tie bolts 36 threadedly engaged at their forward ends with nuts 64 within the hollow frame 15 and provided with securing nuts 38 at the rearward ends thereof which engage and secure the head 35. The tie bolts 36 have shoulders 31 formed on the forward ends thereof and are thereby adapted to secure the liner I9 to the hollow frame 15, a gasket 40 providing a hermetic seal between these two parts. Suitable insulation such as rock wool, transcite, or the like is fastened to the pressure wall around the boiler 23 and prevents the excessive escape of heat therefrom. The foregoing features of construction are best seen in Figs. 2 and 5.

'Boiler heat is provided by a pair of immersion heaters 26 and 26a, located in the sump 24 and secured in a terminal block 8|. The terminal block 8| is secured by bolts (not shown) to the pressure head 35, the heaters 26 projecting through an opening in the head and into the sump 24. A gasket 82 between the terminal block 8| and the head 35 assures an hermetic seal at this point. The heaters 26 are provided with terminals 32 for electric connection thereto, the terminals being covered by a cup-shaped housing 33 screwed to the back plate 13 as seen in Fig. 2.

As will be described later herein, the heaters are thermostatically controlled, to produce steam at a predetermined and adjustable temperature.

The construction just described makes possible the easy removal of the liner I9. By removing the back cover plate 13 and the nuts 38, the head 35 may be removed, revealing the liner, which may then be removed by unscrewing the tie bolts 36 from the forward nuts 64 in the frame 15.

When the device is in operation, sterilizing steamv produced in the boiler sump 24 rises in the inner space between the liner |9 and the pressure wall 25 and enters the chamber I0 through an opening 20 in the top rear wall of the liner I9. Steam @passes through the chamber In in a forward and downward direction as indicated by the arrows in Fig. 2, and escapes from the chamber through a series of exit ports 2| in the hollow frame 15 as best seen in Fig. 5. .As will be seen in Fig. 5, the exit ports 2| carry the steam into the interior of the hollow frame 15 whence it travels upwardly through the frame and exits therefrom through Various communicating passages shown in Fig. 3, and to be described in detail hereinafter.

Each of the nuts 64 secured within the hollow frame 15, is, as shown in Fig. 5, provided with an annular groove 19 in its periphery and thereby does not materially obstruct the interior passage within the frame 15.

The steam exiting from the hollow frame 15 discharges selectively through either or both of a pair of pipes 61 and 68, best seen in Fig, 4, into a condenser tube 42 which is-immersed in a cold water reservoir 4|. The steam condenses in the tube 42 and flows from the upturned end thereof into the reservoir 4|. The reservoir is provided with a lling cover 45 and a float 93 operated level indicator 44, whichprojects through the top of the apparatus in position to be viewed from the front thereof.

For a detailed description of the various control and indicating means relating to the discharge of steam from the sterilizing chamber l0, reference should now be had to Figs. 3 and 4. Mounted to the top of the frame 15 is the hermetically enclosed thermostatic valve 59, the details of which are shown in Fig. 3. The valve 59 includes a valve needle 50 supported on the lower end of the thermostatic bellows 5| of conventional design. The needle 59 is positioned to seat in a valve seat 55 which communicates with the forward end of the pipe 68. A passage 52 provides communication between the interior of the frame 15 and a chamber 54 surrounding the bellows 5| which is lled with a liquid or a gas in the conventional manner so that when heated it expands in a manner to force the needle 5l into closing engagement with the seat 55. The temperature characteristics of the material filling the bellows 5I are such that at temperatures less than that required for adequate sterilization (approximately 250o F.) the valve 59 is open, permitting the escape of air from the frame 15 through the passage 52, the chamber 54, and the seat 55 into the pipe B8. As the temperature in the chamber 54 rises, the bellows 5| expand closing the needle 50 into the seat 55 and preventing further discharge of steam therethrough. The purpose of this arrangement is to allow steam produced in the boiler 23 to force all relatively low temperature air out of the chamber I9 and through the condenser tube 42 thus assuring that the chamber I0 is lled with relatively high temperature steam before the required sterilizing pressure starts to build up in the chamber.

If as is sometimes the case it is desired to discharge the steam manually from the chamber l0 a valve 51 is provided for this purpose. As will be seen in Fig. 3, it serves to control communication between the passage 52 and the pipe 68 through a by-pass including two passages 53 and 56.

A conventional pressure gauge 6| visible from the front of the device is mounted to the top of the frame 15 and communicates therewith through passage 60.

A connection block is also mounted to the top of the frame 15 and has formed therein a passage 62 which communicates with the pipe 61 as seen in Fig. 3, and also with a conventional spring loaded safety valve 63 which operates to release excessive steam pressure should the same build up in the chamber I0. As will be seen from an examination of Fig. 4, the pipe 51 communicates with the condenser tube 42 through a solenoid operated valve 69, the electrical circuit of which is interconnected with other electrical controls to be described hereinafter. When the solenoid valve'69 is opened, steam may discharge through the frame 15, the connection block Sil, and the pipe 61 into the condenser tube d2. As can be seen in Fig. 6 an indicator light 92 is ccnnected in parallel with the valve 69 and serves to indicate when steam is discharging through valve 69.

`mostats 21 and 21a which are mounted in the forward vertical wall of tliesump 24 and project into the interior thereof. The thermostats 21 and 21a and heaters 26 and 26a are connected in series-parallel as shown in Fig. 6. One of the heaters 26 is controlled by a thermostat 21 having a fixed setting slightly less-than the lowest desired sterilization temperature. The other heater 26a is controlled by an adjustable thermostat 21a. The thermostats 21 and 21a may be of the liquid-filled, gas-filled bi-Inetal or other suitable variety and one of them, 21a, is provided With a control knob 28 mounted on the front cover plate 16 and connected to the thermostat through a shaft 29 and a pair of universal joints 36. The purpose of the control knob 28 is to adjust the thermostat 21a to cut off the supply of electric current to one of the heaters 26 when the temperature in the boiler sump 24 reaches a desired and predetermined level.

The advantage of the dual heater arrangement is that during the initial heating period when the demand for heat is high, this high demand is met by both heaters acting in unison. There-` after, it is only necessary to maintain the steam chamber at a xed temperature and the heat required is only that which is lost by conduction through the insulation and radiation from the outer housing. It is of considerable advantage to make use of a heater whichhas a maximum capacity only slightly greater than the demand since, for one thing, only a relatively small current need pass through the contacts of the controlling thermostat, and for another, wide variations in temperature during the on-off, heat- 'ing cycle are avoided. These wide variations in regulated temperature are known as overshooting and have been a particular disadvantage in previous apparatus of the class described since it is of extreme importance that the sterilizing tem-- perature be maintained substantially constant. Insuncient temperature will fail to produce efvfective sterilization and excessive temperature may result in damage to surgical apparel, particularly rubber gloves and the like. I have found that with the control system of my invention, autoclave temperatures may readily 'be controlled within a maximum dierential of 3, whereas differentials of or more are frequently encountered in previous apparatus.

Delivery of electric current to the heaters 26 and 26a is also controlled by means of a single pole double throw switch 3| which is mounted in the lower portion of the front cover plate 16 as seen in Fig. l. Operation of the switch 3| also controls the delivery of electric current to the solenoid valve 69 as will be seen from an examination of the wiring diagram shown in Fig. 6, where it will be seen that when the switch is operated to turn oi the heaters 26 and 26o, it simultaneously energizes the solenoid 69 thereby permitting steam to discharge through the pipe 61 and into the condenser tube 42 as previously described. Thus, when the steam is discharged from the chamber |0 by operation of the switch 3|, preparatory to opening the door and removing sterilized material from the chamber |0, the heaters 26 are automatically shut oif, and the possibility of boiling away of the water in the sump 24 is substantially obviated.

As the supply of water in the sump 24 becomes depleted and the level therein drops, a conventional hingedly mounted float 48 swings downwardly opening a valve 49 andV permitting waterffrom the 'reservoir 4l to flow downwardly through :a check valve '46. a tube 41, and the 6 float operated valve 49 into the sump 24 thus replenishing the supply of water therein. The check valve 46 prevents steam from escaping back up the tube 41 into the reservoir 4|, thus water can flow through the tube 41 when the boiler is substantially at atmospheric pressure.

It is obvious that continuous operation of the device will result in loss of water in the reservoir 4|, due to the escape of steam from the chamber l0 each time the door is opened. To replenish the water thus lost, the lling cap is provided through which the reservoir 4| may be relled as previously described.

The autoclave embodying my invention is operated in the following manner:

Having ascertained by an examination of the scale 44 that there is suincient water in the reservoir 4|, the latch 12 is disengaged from the strong back I2, which is then swung back carrying with it the door and giving access to the chamber I6. The material to be sterilized is then placed in the chamber IU, the door closed and locked, and pressure is applied thereto by means of the hand wheel |4 and the pressure screw |3. It will be noted that the locking of the latch 12 automatically closes the line switch 96 thus placing the heaters under the sole control of the control switch 3|. The thermostat 21a is adjusted by means of control knob 28 to give the desired temperature of sterilization, and the switch 3| is then operated to the on position thus delivering current to the heaters 26. As steam is produced in the sump 24 it passes through the chamber I0 in the manner previously described, operates the thermostatic valve 59, and builds up pressure in the chamber |(l. The apparatus is left in this condition for a period of time necessary to eiect the desired sterilization of the material in the chamber l0, at which point switch 3| is operated to the discharge position. As previously described, this turns off the heaters 26 and allows the discharge of the steam from the chamber l0. When the steam has been discharged from the chamber |0 as will be indicated by the gauge 6| the door may be opened and the sterilized material removed.

Should it become necessary to manually discharge the steam from the chamber I9 by reason, for example, of an electric power failure, it may be accomplished through manipulation of the valve 5l' in the manner previously described.

It will be appreciated by those familiar with operation of equipment of the class described, that since the walls of the hollow frame 15 are to all intents and purposes, integral with the pressure wall 25, it is maintained at substantially the same temperature as the steam in chamber |3 and hence there is little or no tendency for steam to condense within the frame 15.

It is also obvious that steam entering the frame 15 may reach the discharge passages 52, and 62 by passing upwardly through either of the vertical portions of the frame '15. Thus since a multiple passage is formed there is less likelihood of plugging the same and preventing discharge of steam from the chamber l0.

It will be noted further that, if the thermostat 21 should, for some reason, fail to control the heaters 26, resulting in the production of excessive pressures within the chamber l0 and the balance of the system communicating therewith, the safety valve 63 will operate to release steam thus reducing such excessive pressure.

While the apparatus shown and described herein is fully capable of achieving the objects 7. and providing the advantages hereinbefore stated, it is subject to considerable modiiication within the spirit of the invention and therefore I do not mean to be limited to the form shown and described herein, but rather to the scope of the appended claims.

I claim:

1. In an autoclave, the combination of: a pressure chamber having an opening therein adapted to receive material for sterilization in said chamber; a hollow frame for said opening having a passage therein communicating with said chamber; means to hermetically close said opening; means for producing live steam in said chamber; and means operatively associated with said frame to control the discharge of steam from said passage.

2. In an autoclave, the combination of: a live steam chamber adapted to receive material for sterilization therein; means in a vertical wall in said chamber forming a hollow and substantially rectilinear door frame therein, said frame having a passage throughout the peripheral length thereof having communication with said chamber adjacent the bottom edge of said frame; and valve means mounted to the top edge of said frame and having communication with the passage therein, said valve means being adapted to control the discharge of steam from said chamber through said passage.

3. In an autoclave, the combination of means forming a pressure chamber adapted to receive material for sterilization therein; means including-a water sump in said chamber and a heater in said sump to produce steam in said chamber; operable means to discharge steam from said chamber; and means responsive to operation of said discharge means to disable said heater.

4. In an autoclave, the combination of: means forming a pressure chamber adapted to contain live steam; means including a water sump in said chamber and a heater in said sump to produce steam in saidchamber; an electrically operated discharge valve for said chamber; and current control means for said heater and valve adapted to selectively disconnect the former upon opening of the latter or energize the former upon closing of the latter.

5. In an autoclave, the combination of: means forming a pressure chamber adapted to receive material for sterilization therein; means including a water sump in said chamber and a heater in said sump to produce steam in said chamber;

- a Water supply reservoir; passage forming means to discharge water from said reservoir into said sump; and control means in said passage means responsive to water level in said sump to control said discharge.

6. In an autoclave, the combination of: means forming a pressure chamber adapted to receive material for sterilization therein; means including a water sump in said chamber and a heater in said sump to produce steam in said chamber; a water supply reservoir; a water tube connected between said reservoir and sump to replenish the water supply in said sump; and a check valve in said tube to prevent passage of steam from said chamber to said reservoir.

7. In an autoclave, the combination of t means forming a pressure chamber adapted to receive material for sterilization therein and a, water sump therein; a pair of heaters in said sump adapted to convert water therein into live steam in said chamber; 9, water supply reservoir; steam passage means formed in a wallI of said pressure chamber adapted to discharge steam therefrom; a condenser tube having communication with said steam passage means and positioned in said reservoir whereby to be immersed in water therein; and thermostatic means operatively associated with said heaters whereby one of the same is adapted to steadily deliver a portion of the heat necessary to produce said live steam and the other adapted to intermittently deliver sucient heat to maintain the temperature of said steam substantially constant.

8. In an autoclave, the combination of: a pressure chamber having a water sump and heater in said sump to produce live steam in said chamber; a removable compartment Within said chamber adapted to receive material for sterilization by said steam; means forming an opening with a pressure door in a Wall of said chamber adapted to admit said material into said compartment; a hollow frame formed in a wall of said chamber surrounding said opening and having a passage therein communicating with said compartment; and valve means operatively associated with said frame whereby to control the discharge of steam from said compartment through said passage.

9. In an autoclave, the combination of: means for producing live steam; a chamber adapted to receive material for sterilization by said steam; means for hermetically closing said chamber; passage forming means integral with the wall of said chamber adapted to carry steam from said chamber; and valve means including a safety valve adapted to control the discharge of steam through said passage.

10. In an autoclave, the combination of means forming a pressure chamber having a steam discharge passage formed integrally with a Wall thereof; means including a Water sump in said chamber and an electric heater in said sump to produce steam in said chamber; thermostatic control means for said heater adapted to control the pressure of steam in said chamber; and means including a valve in said passage and a switch connected to control said heater, saidl valve and switch being interconnected so that said valve is opened upon the de-energizing of said electric heater.

11. In an autoclave, the combination of: means forming an insulated pressure chamber with a Water sump therein; means forming av passage in a wall of said chamber opening thereinto; a water supply reservoir; a condenser tube positioned in said reservoir and adapted to communicate with said passage; valve means between said passage and condenser tube adapted to control said communication; a water tube connected between said reservoir and said sump adapted to deliver water to said sump; heater means in said sump adapted to convert water therein into live steam at a predetermined pressure; a iioat valve responsive to water level in said sump to control water flow through said tube; and a check valve in said tube adapted to prevent counterlow therethrough due to pressure of said steam.

12. In an autoclave, the combination of: means forming an insulated pressure chamber having a Water sump; means forming a passage in a wall of said chamber opening thereinto; a water supply reservoir; a condenser tube positioned in said reservoir and adapted to communicate with said passage; valve means, including a solenoid valve, between said passage and condenser tube adapted to control said communication; a water supply tube connected between said reservoir and said sump; an electric heater to Y control element for each heater in said sump adapted to produce live steam at a predetermined pressure in said chamber; a float valve responsive to Water level in said sump to control Water flow through said supply tube; a. check valve in said supply tube adapted to prevent counter-flow therethrough due to pressure of said steam; and switch means connected between said heater and solenoid valve adapted to disconnect the former upon opening thelatter.

13. In an-autoclave the combination of: means forming a pressure chamber adapted to receive material for sterilization therein; boiler means including a pair of heaters adapted to produce steam for delivery to said chamber; thermostatic means including separately adjustable sensing elements connected to each of said heaters whereby one of said heaters is adapted to deliver an amount of the heat necessary to initially heat said chamber to a predetermined temperature, and the other of said heaters is adapted to intermittently deliver an amount of the heat necessary to maintain said chamber always above said predetermined temperature.

14. In an autoclave, the combination of: means forming a pressure chamber adapted to receive material for sterilization therein; a boiler adapted to produce live steam for delivery to said pressure chamber; a pair of heaters for said boiler; first thermostatic control means operatively connected with a first of said heaters whereby the same is adapted to raise said boiler means to a temperature slightly less than that desired for sterilization; and second separately adjustable thermostatic control means operatively connected with the other of said heaters whereby the same is adapted to increase said temperature over that produced by said rst a degree desired for sterilization.

15. In an autoclave, the combination of: a pressure chamber adapted to contain live steam; removable liner means forming an inner compartment ,in said chamber adapted to receive material for sterilization therein; means forming a passage integral with a wall of said chamber adapted to discharge steam from said compartment; valve means in said passage to control said discharge; boiler means including a pair of 'heaters adapted to produce steam for delivery into said compartment; discharge control means adapted to selectively open said valve means While disabling said heaters or to energize said heaters upon closingsaid valve means; thermostatic means including a separately adjustable of said heaters whereby one of the same is adapted to initially heat said boiler means to a predetermined temperature and the other to intermittently deliver heat to said boiler means, whereby to maintain the same at a relatively constant temperature of sterilization; and water supply means for said boiler means responsive to the water level therein to deliver water thereto through said supply means including a check valve to prevent counter-flow therethrough due to pressure of steam in said boiler means.

16. In an autoclave, the combination of: means forming a pressure chamber having live steam therein, said chamber having a rectangular forward opening, a rear opening, a removable pressure head secured in said rear opening normally to close the same, and a hinged door for said forward opening; and a liner for said Y hermetically seal said passageway; and valve means in said 10 chamber having a, generally rectilinear crosssection whereby the same is. adapted for alignment with said forward opening to receive generally rectilinear packs of material for sterilization in said liner, the latter being removably secured to the inner wall of said pressure chamber adjacent the edges of said forward opening and forming a sterilization chamber Within said pressure chamber, the transverse and vertical dimensions of said liner being less than those of said rear opening whereby said liner may be removed and inserted through saidrear opening.

17. In an autoclave, the combination of; Ya pressure chamber having a loading opening to receive material for sterilization in said chamber and a movable closure for said opening to hermetically seal said chamber; means including a water sump in said chamber and a heater in said sump to produce steam in said chamber; and means responsive to the movement of said closure to disable said heater when said chamber is unsealed.

18. The construction of claim 17 further characterized in that said heater is electric and said disabling means includes connected to said closure.

19. In an autoclave, the combination of: a pressure chamber having an opening therein adapted to receive material for sterilization in said chamber; a removable liner in said chamber spaced from the walls thereof and aligned with said opening to receive said material therethrough for support in said liner during said sterilization, said liner having an opening to receive steam from said chamber; a hollow frame for said opening having a passage therein communicating with the interior of said liner to discharge steam therefrom; means to hermetically close said opening; means for producing live steam in said chamber; and means operatively associated with said frame to control the discharge of steam from said passage.

20. In an autoclave, the combination of: a live steam chamber having a vertical wall and an opening in said wall to receive material to be sterilized; a liner in said chamber removably secured to said wall, spaced from the other walls of said chamber, and aligned with said opening to receive said material for sterilization in said liner, the latter having a top opening to receive steam from said chamber; closure means to opening; means forming a passageway in said first chamber wall, said passageway having an opening into said liner adjacent the bottom thereof to discharge steam therefrom, said passageway being in intimate heat transfer contact with said first wall whereby to inhibit the condensation of steam in said passageway to control said discharge of steam.

EMIL R. SCHIPANSIQI.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS a switch mechanically 

